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Optimal MAC based cooperative spectrum sensing in cognitive radio networks

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science{1.(Information sciences) 2012年第6期55卷 1388-1396页

作者： CHEN Zhong 1.zhang XianDa 1.& {1. LanJuan 2 1.State Key {1. of Intelligent technology and Systems,Tsinghua national {1. for Information science and technology,Department of Automation,Tsinghua university,Beijing 1.0084,china 2 Institute of Command Automation,PLA university of science and technology,Nanjing 21.007,china 1. State Key laboratory of Intelligent{1. and Systems Tsinghua National Laboratory for Information Science and Technology Department of Automation Tsinghua University Beijing 100084 China2. Institute of Command Automation PLA University of Science and Technology Nanjing 210007 China

This paper considers a cognitive radio (CR) system in non-ideal fading wireless channels and pro-poses cooperative spectrum sensing schemes based on coherent multiple access channels (MAC),serving as an alternative way to improve the cooperative spectrum sensing performance and provide space diversity for spec-trum *** statistics are transmitted using a common channel from the secondary users (SUs) to a fusion center (FC) where the global decision is *** optimal scaling factors of the proposed schemes are obtained by maximizing the detection probability under a target false alarm probability and a transmit power *** the proposed optimal MAC scheme has high computational complexity,a sub-optimal solu-tion based on maximization of the deflection coefficient (DC) is also *** results show that the proposed algorithms can significantly improve the spectrum sensing performance and approach the detection baseline.

关键词： cognitive radio (CR) spectrum sensing multiple access channel (MAC) deflection coefficient optimization

Characteristics and origins of primary fluids and noble gases in mantle-derived minerals from the Yishu area,Shandong Province,china

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science{1. Earth sciences 2006年第1期49卷 77-87页

作者： MA jinlong1.2, TAO Mingxin2,3 & YE Xianren2 1. Resources and Environmental School, Lanzhou{1., Lanzhou 730000, china 2. Key laboratory of Gas Geochemistry, Institute of Geology and Geophysics, Chinese Academy of sciences, Lanzhou 730000, china 3. College of Resources science & technology, Beijing Normal{1., Beijing 1.0875, china 1. Resources and Environmental School Lanzhou University Lanzhou 730000 China 2. Key laboratory of Gas Geochemistry Institute of Geology and Geophysics Chinese Academy of Sciences Lanzhou 730000 China 3. College of Resources science &{1. Beijing Normal University Beijing 100875 China

Fluids and noble gases of mantle-derived materials are important tracers forthe mantle information. Compositions of primary fluids and noble gases in mantle-derived mineralsfrom the Yishu area, Shandong Province, china, were tested by the methods of heat-bursting andheat-melting respectively. The fluids are mainly composed of CO_2, CO and H_2, which account forabout 90% of the total, and are similar to the mantle-derived rocks from other areas of easternchina; ratios of ~3He/~4He in almost all samples range from 0.82 Ra to 2.74 Ra, whereas^(40)Ar/^(36)Ar from 299.5 to 758.8. Both ranges are much lower than those of the typical oceanmantle-derived samples (such as MORB) and primarily reflect the influences of the atmosphericcomponents and the radiogenic isotopes. Ratios of C/~3He range from 27.6 x 1.~9 to 1.50 x 1.~9,N_2/Ar from 927 to 5661., and N_2/~3He from 2.5 x 1.~9 to 27 x 1.~9, similar to those in westernUnited States and New Zealand which belong to the tectonic plate collision regions. The ratios fallin the intersect of mantle-crust-atmosphere in the comprehensive tracer-charts, reflecting theinfluences of the atmosphere and the crusts with organic components. Our results suggest that thecomposition of the primary fluids and the isotopic ratios of the noble gases may either reflect theevolution process of mantle-derived rocks connected with the rise and eruption of magma, or theinfluence of the ancient subduction-plate on the continental mantle of this region.

关键词： noble gases, primary fluids, mantle-derived minerals, Yishu area.

Characterization of MASDs of surface soils in north china and its influence on estimating dust emission

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Chinese science Bulletin 2004年第20期49卷 2169-2176页

作者： MEI Fanmin1.2, zhang Xiaoye1. LU Huayu1. SHEN Zhenxing1.& WANG Yaqiang1.1. State Key{1. of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of sciences, Xian 71.075, china 2. Xian university of Engineering science and technology, Xian 71.048, china State Key laboratory of Loess and Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi''an 710075 China Xi''an university of Engineering{1. and technology Xi''an 710048 China

The micro-aggregated size distribution (MASD) of surface soil is an important parameter for modelling dust emission. However, there is no dataset of MASDs of all sur-face soil types in north china. The MASDs are here pre-sented, measured by dry sieving, for typical surface soil sam-ples, including sandy soil, gravelly sand soil, gravelly loam soil, loam soil and silt loam soil, collected from sandy deserts, Gobi deserts, oases, farmlands in steppe regions and steppe areas in north china. The MASDs of various surface soil types exhibit a combination of several log-normal distribu-tions of five separated sizes with mean mass median diame-ters (MMDs) of 90, 21., 390, 600 and 980 mm, respectively, and mean standard deviations (SDs) of 1.25, 1.40, 1.25, 1.35 and 1.25 respectively. The log-normal distributions corre-spond to very fine sand, fine sand, medium sand, coarse sand and very coarse sand population. On the basis of characteri-zation of the retrieved MASDs of various surface soil types in north china, dust emission fluxes are modelled by a dust production model (DPM model). It is shown that dust emis-sion has been significantly influenced by MASDs. Fine sand and very fine sand are always associated with the highest dust emission fluxes. Emission fluxes of the medium sand, gravelly sand soil, gravelly loam soil and loam soil are lower than those of very fine sand and fine sand, but larger than those of the coarse sand. The differences in dust emission fluxes vary among the different soil types from 1.1.to 1.3 mg·m-2·s-1. Dust emission fluxes from sandy deserts and farmlands covered with sand sheets in north china rang from 1.1.to 1.4 mg·m-2·s-1.while those from Gobi deserts, farmlands and steppes with gravelly desertification range from 1.1.to 1.2 mg·m-2· s-1. The modelled results indicate that deserts and farmlands with sand are the major dust sources in north china.

关键词：华北地区 MASDs 微块状粒度分布地面土壤粉尘排放壤土大气污染气溶胶

SQUARE attack on block ciphers with low algebraic degree

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science{1.(Information sciences) 2010年第10期53卷 1988-1995页

作者： SUN Bing 1., LI RuiLin 1., QU LongJiang 1.3 & LI Chao 1.2,3 1.science College of{1. university of Defense technology, Changsha 41.073, china 2 State Key laboratory of Information Security, Graduate university of Chinese Academy of sciences, Beijing 1.0049, china 3{1. Mobile Communications Research laboratory, Southeast university, Nanjing 21.096, china 1. science College of{1. university of Defense technology Changsha 410073 China3. National Mobile Communications Research Laboratory Southeast University Nanjing 210096 China2. State Key Laboratory of Information Security Graduate University of Chinese Academy of Sciences Beijing 100049 China

By using an algebraic method, the mathematical foundation of SQUARE attack is studied in this paper. We point out that a SQUARE distinguisher exists if and only if the degree of the polynomial function between n-bit input which is active and n-bit output which is balanced is 2 n-2. And the algebraic method can also be used to determine the property of a balanced set after passed through a nonlinear S-box, by which in some cases we can find a SQUARE distinguisher with more rounds. The validity of SQUARE attack and the influence of the choice of S-box are also studied. If the round function of a Feistel cipher has a low algebraic degree, a SQUARE attack cannot recover the right keys in some special cases. However, SQUARE attack on SPN ciphers always holds. The relations among SQUARE attack and some other cryptanalytic method are studied, showing that if a cipher is breakable by SQUARE attack, then it is also breakable by the interpolation attack.

关键词： SQUARE attack interpolation attack integral attack block cipher

High-sensitivity photovoltage based on the interfacial photoelectric effect in the SrTiO_(3-δ)/Si heterojunction

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science{1.(Physics,Mechanics & Astronomy) 2010年第11期53卷 2080-2083页

作者： WEN Juan 1.GUO HaiZhong 1.XING Jie 2,Lü HuiBin 1.JIN Kui-Juan 1.HE Meng 1.& yang GuoZhen 1.1.Beijing {1. {1. for Condensed Matter Physics,Institute of Physics,Chinese Academy of sciences,Beijing 1.01.0,china 2 School of Materials sciences and technology,china university of Geosciences,Beijing 1.0083,china 1. Beijing national{1. for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China2. School of Materials Sciences and Technology China University of Geosciences Beijing 100083 China

A high sensitivity photovoltaic effect has been observed in a heterojunction composed of n-type wide bandgap oxide SrTiO 3-δ and p-type Si fabricated by laser molecular beam *** responsivity of open-circuit photovoltage can reach 1. 4 V/W without any amplification under zero bias for the wavelength range from visible to near infrared light in nW-μW *** attribute the high performance of the photovoltage responsivity to the interfacial photoelectric effects in the SrTiO 3-δ /Si *** the experimental results,some ideas can be generalized to improve photovoltaic efficiency and develop high sensitivity photodetectors with wide bandgap oxide materials and Si.

关键词： SrTiO 3-δ/Si heterojunction interfacial photoelectric effect photovoltage

Morphologies of Fe-66.7 at.%Si alloy solidified in a drop tube

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science{1.(Physics,Mechanics & Astronomy) 2005年第6期48卷 658-666页

作者： WANG Haiyan1.2, LIU Riping1. MA Mingzhen1. JING Qin1. LI Gong1. SUN Liling2 & WANG Wenkui1.2 1. Key laboratory of Metastable Materials{1. & technology, Yanshan university, Qinhuangdao 066004, china 2. Institute of Physics, Chinese Academy of sciences, Beijing 1.0080, china 1. Key laboratory of Metastable Materials{1. & technology Yanshan University 066004 Qinhuangdao China 2. Institute of Physics Chinese Academy of Sciences 100080 Beijing China

Solidification of 0.1.1.0 mm diameter droplets of Fe-66.7 at.%Si alloy was achieved in a 3 m drop tube. The XRD, EDS, and SEM measurements reveal that all the droplets are composed of the primary phase α and the α+ε eutectic. With decreasing droplet diameter, the growth mode of the primary phase α changes from faceted to nonfaceted growth and the eutectic changes from needle-like to anomalous eutectic. In addition, the width of the primary phase α decreases with decreasing droplet size. The different cooling rates and undercooling levels corresponding to the samples with different sizes are responsible for the morphology changes. The cooling rates of the samples with different diameters during free fall were calculated and their effects on the microstructure formation were discussed. This kind of transition is also found inside the same sample, which is due to the larger cooling rate on the surface than at the center.

关键词： Fe-Si alloy, solidification, drop tube, undercooling.

Statistical theory for hydrogen bonding fluid system of A_aD_d type (I): The geometrical phase transition

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science{1. Chemistry 2006年第6期49卷 499-506页

作者： WANG Haijun1.2, HONG Xiaozhong3, GU Fang1.& BA Xinwu1.1. College of Chemistry and Environment science, Hebei{1., Baoding 071.02, china 2. International Center for Materials Physics, Chinese Academy of sciences, Shenyang 1.001., china 3. College of Physics science and technology, Hebei{1., Baoding 071.02, china 1. College of Chemistry and Environment science Hebei University Baoding 071002 China 2. International Center for Materials Physics Chinese Academy of Sciences Shenyang 110016 China 3. College of Physics science and{1. Hebei University Baoding 071002 China

The influence of hydrogen bonds on the physical and chemical properties of hydrogen bonding fluid system of AaDd type is investigated from two viewpoints by the principle of statistical mechanics. In detail, we proposed two new ways that can be used to obtain the equilibrium size distribution of the hydrogen bonding clusters, and derived the analytical expression of a relationship between the hydrogen bonding free energy and hydrogen bonding degree. For the nonlinear hydrogen bonding systems, it is shown that the sol-gel phase transition can take place under proper conditions, which is further proven to be a kind of geometrical phase transition rather than a thermodynamic one. Moreover, several problems associated with the geometrical phase transition and liquid-solid phase transition in nonlinear hydrogen bonding systems are discussed.

关键词： hydrogen bonding fluid, equilibrium free energy, geometrical phase transition.

Density functional theory study of the magnetic properties of rare earth complexes:the magnetic coupling mechanism in Y~Ⅲ and Gd~Ⅲ complexes with nitronyl nitroxide

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science{1. Chemistry 2009年第11期52卷 1961-1968页

作者： REN Jie1.2,WANG BingWu1.& CHEN ZhiDa1.1.Beijing national{1. for Molecular sciences,State Key{1. of Rare Earth Materials Chemistry and Applications,College of Chemistry and Molecular Engineering,Peking university,Beijing 1.0871.china 2 College of science,Hebei university of science and technology,Shijiazhuang 05001.,china 1. Beijing national{1. for Molecular sciences State Key Laboratory of Rare Earth Materials Chemistry and Applications College of Chemistry and Molecular Engineering Peking University Beijing 100871 China 2. College of science Hebei University of Science and Technology Shijiazhuang 050018 China

The magnetic coupling interactions of the nitronyl nitroxide radicals bound to diamagnetic(YⅢ) and paramagnetic(GdⅢ) rare earth ions in two model magnetic systems based on novel rare earth organic radical complexes Ln(hfac)3(NITPhOCH3)2(Ln=YⅢ 1.GdⅢ 2;hafc = hexafluoroacetylacetonate;NIT-PhOCH3 = 4'-methoxyo-phenyl-4,4,5,5-tetramethylimidazoline-1.oxyl-3-oxide) have been investigated by density functional theory(DFT).The magnetic coupling mechanisms were also explored from the viewpoint of molecular orbital and spin density *** calculations show that the empty 4d-orbitals of YⅢ and 5d-orbitals of GdⅢ play an important role in the antiferromagnetic coupling between the two nitronyl nitroxide radical ligands,and that the ferromagnetic coupling between the GdⅢ ion and the radical magnetic centers can be attributed to the nearly complete localization of the isotropic 4f-shell and singly occupied magnetic orbital(π) of the nitronyl nitroxide.

关键词： magnetic coupling density functional theory rare earth ion gadolinium(Ⅲ) complexes yttrium(Ⅲ) complexes

Analysis of a kind of quantum cryptographic schemes based on secret sharing

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science{1.(Physics,Mechanics & Astronomy) 2009年第9期52卷 1313-1316页

作者： zhang XingLan1.& JI DongYao2 1.College of Computer{1. and technology, Beijing university of technology, Beijing 1.01.4, china 2 State Key laboratory of Information Security, Graduate university of Chinese Academy of sciences, Beijing 1.0049, china College of Computer science and{1. Beijing University of Technology Beijing 100124 China State Key laboratory of Information Security Graduate University of Chinese Academy of Sciences Beijing 100049 China

Recently, yang et al. proposed a kind of quantum cryptographic schemes based on secret sharing. The main idea is drawn from the case, where any n participants who share a secret K can co-operate as K does. This process can be applied to encryption, authentication, signature and so on. Unfortunately, since there is no identity authentication of the share's holder, these schemes inherit the limitation of secret sharing in practice. If some participants do not follow the protocol, the protocol would be a failure at last. Moreover, these schemes encounter another serious attack. Any two participants can co-operate to defeat the schemes by sending different shares to the parties unknown to the distributor of the secret K, such that these parties can execute the protocol as well. The attack proves that it is not enough for quantum cryptographic schemes that only the secret key is secure.

关键词： quantum identity authentication quantum secure direct communication quantum signature secret sharing